Method for the production of iron oxide from ferrous solutions



either a; canb Patented Oct. 20, 1953 pl murnop ron PRODUCTION OF mowOXITBE FRQM FERRQHS. tress Charles @urti's ('llarke, Grove City, Pa.,assignor to WHeatIand Tube Company, Wheatiand Pa acnrporatfon ofPennsylvania oDrawiuet A in i ti nJanuar r-ZG', 951,,

Serial No. 208,080 I 2* Claims; (01. iocwson This invention relates to amethod for the production of iron oxide from liquors having a ferrouscontent; such as spent pickling acid; spent in the pickling of ironor'steel. 1 Almost anyfer's rous solution will serve as; the initi'a];material;

The term iron oxide as employed herein, is: intended to compriseacombinati'onof ferric oxide Fe'zQc magnetite- FeQOi, and limonitm Theiron oxide produced in accordance with this invention maybe'producedinvarious colors, as yellows; reds, browns and blacks; and; having variousundertones.

Th p ducts W lli be ound. s cial y adaptable.- for use as pigments, I

Broadlyspeaking, accordance with the. method of this invention, aliquor, having a forrims co t; wi l e e n d by ad'i stment oi,

t pH to ffec he or ation of rud: which. is separated from: the clean maybe calcined for the production of, aniinpure iron.

mmspecificellr h pent nzqusrwilr be treats d fin? he ati nof e cru bx"heat ng n e autoclave t a tem erature betweenabout 50 E i-200 F1, andadding an alkali fo exampla as acarbonatei bicarbonate, lime or otheralkali in sufficient quantity to effect the f rmation of. the crud. Theformation th crud will be determined visually, but generally formswithin the range ofabout pH 2EO-pH 6.0. Whenthe crud has formed, it isseparated from he: clean liquor, The cleamliquor is transferred into an:autoclave and heated to. a temperature: of abou -2" ...enen iine up n tcolor d im; he: iron Oxide product; A, carbonate; hicarbonata, a;mixture thereof; on a mixture of onate or abicanbonafieg. or a mixturethereot. Wth analkaliis then added to the autolass quantity to adjustthe pH to Within about the range, Maps;- 124).

As has been indicated, the color of the iron oxideproduct of themethod'of this. invention are yellows; reds, browns and blacks: Thesevarious colors and the shades thereof are produced by a combination ofthe precipitation temperature and the pH of the ferrous slurry. At thelower precipitation temperatures and in the lower pH range, the colorswill be in the yellow range, while in the higher precipitationtemperatures 2- t and. in the higher pH; range; the: colors he in the.black range. Reds and browns are prone duce'ct at intermedi'auevprecipitation temperatures and in intermediate pH ranges.r

When the; required; pH range is obtained the temperature. is raised towithin; about range: 150 450? F:

When the required; temperature is. reached, an; oxidizinggas, as, forexample, air,- oxygen: or'the: like,- is introduced at a rate: withmabout range +5D02 cubic feet per minute. The faster: thev rate at whichthe oxidizing gas is introduced the finer will be the: particles of theiron oxide product.

The internal pressure-in the autociavc during" the. oxidation period:will be within the range 0-70 pounds per square-inch Here it will benoted that the pressurev during oxidation will determine the undertoneof the color of the iron oxide product;

When the oxidation teen ca ried on: a e sonable l n h or time thecontents of the auto la e w ll? be che ked hr the ac d; test to ale-.-srm uie Wh her th conve s n; oi. the ferrous lurry t ir n o d i com-nWhen the 6.011s: ve s ns comple e, the oxidizing? wilt. be: shut L theiron oxid pump d to. a; wast-line: tank! washed; until.- the: solublesalt content is, red ced. to Within: ailowahlelimitsl sari oneshalfi tone per cent- T e washed irom oxide; filtered; and the filter cakedried-l to less han ne: per tree; moisture; The: dried 1 m oxide s: thenr ader for use:

The: following. examples will; be: more cailyillustratiuezof thecarrying out of: the nretln dd accordance-with this inventibn zi oduc onofmedium: red pure; iron: oxide; blue brown undertone A: clean. termolution is pumped intzr a lined au ocl ve in the amount of.approximately 9 allons Ilhe autoclave is them sealed and the ferroussolution is heated to 150 F. mums; point, a soda ash solution at, F. ispumped into the agitated ferrous solution. This pumping iszcontinueduntil a p11 ol '829is reached. Agitation is continued while thetemperature of the errous oarhona eslurm is raised near my Miationi tntipn od whilea t at lQQ-cuhio-ieetmeir minute is diffused through theferrous carbonate slurry and a positive internal pressure of 20 poundsper square inch is maintained. After six hours of oxidation, the slurryis checked by the acid test to determine whether the conversion EXAMPLE2 Production of dark brown oxide with red black undertone A cleanferrous solution is pumped into a glass lined autoclave in the amount ofapproximately 7 1500 gallons. The autoclave is then sealed and ferroussolution is heated to 180 F. At this polnt, a soda ash solution at 145F. is pumped into the agitated ferrous solution. This pumping iscontinued until a pH of 9.61s reached. Agitation continues while thetemperature of the ferrous carbonate slurry is raised to 200 F.Agitation is. continued while air at 150 cubic feet per minute isdiffused through the slurry and a. positive internal pressure of 30pounds per square inch is maintained. After four hours of oxidation, theferrous carbonate slurry is checked by the acid test to determinewhether the conversion of the carbonate slurry to iron oxide iscomplete. If not complete, oxidation is continued until completed. Whenthe oxidation is complete, the air is shut off and the iron oxide ispumped to a washing tank. It is then washed until the soluble saltcontent is less than of 1%. The washed iron oxide is then filtered andthe filter cake is dried to less than 1% free moisture. The dried ironoxide is then bagged.

EXAMPLE 3 Production of black iron oxide with red undertone A cleanferrous solution is pumped into a glass lined autoclave in the amount ofapproximately 1500 gallons. The autoclave is then sealed and theferroussolution heated to 170 F. At this 1500 gallons. The autoclave is thensealed and the ferrous solution is heated to 120 F. At this point, asoda ash or bicarbonate solution at 145 F. is pumped into the agitatedferrous solution. This pumping is continued until a pH of 7.4 isreached. Agitation continues while the temperature of the ferrous slurryis raised to 200 F. Agitation continues while air at 75 C. F. M. isdiffused through the slurry and a positive pressure of 0 p. s. i. g. ismaintained during this oxidation. After 8 hours of oxidation the slurryis checked by the acid test to determine whether the conversion of theferrous slurry to iron oxide is complete. If not complete, oxidation iscontinued until complete. When oxidation is com plete, the air is shutoff and the iron oxide pumped to a washing tank. It is then washed untilthe soluble salt content is less than /2 of 1%. The washed iron oxide isthen filtered and the filter cake dried to less than 1% free moisture.The

point, a solution consisting of a ratio of 3 parts 2:-

caustic soda and 7 parts soda ash, at 145 F., is

pumped into the agitated ferrous solution. This and the iron oxide ispumped to a washing tank.

It is then washed until the soluble salt content isless than /2 of 1%.The washed iron oxide is then filtered and the filter cake dried to lessthan 1% free moisture- The dried iron oxide is then bagged.

i EXAMPLE 4 Production of yellow iron oxide with tan undertone A cleanferrous solution is pumped into a glass lined autoclave in the amount ofapproximately dried iron oxide is then bagged.

What is claimed is:

1. The method of producing a dark brown iron oxide with red-blackundertone from an impure liquor having a ferrous content which comprisesadjusting the pH of the impure liquor to within the range pH 2-pH 6until a crud is formed, separating the crud, adjusting the pH of theresidual liquor to about 9.6, elevating the temperature of the liquor toabout 200 F., introducing an oxidizing gas into the liquor whilemaintaining pressure on the liquor of about 30 pounds per square inchuntil conversion of the ferrous content of the liquor to higher ironoxides is completed, washing the iron oxides and drymg.

2. The method of producing a dark brown iron oxide with red-blackundertone from an impure liquor having a ferrous content which comprisesadjusting the pH of the impure liquor to within the range pH 2-pH 6until a crud is formed, separating the crud, adjusting the pH of theresidual liquor to about 9.6 while maintaining the liquor at atemperature of about 180 thereafter introducing an oxidizinggas into theliquor while maintaining the liquor at a temperature of about 200 F. andmaintaining a pres: sure on" the liquor of about 30 pounds per sq. inchuntil the conversion of the ferrous content of the liquor to higher ironoxides is completed, washing the iron oxides. and drying the ironoxides.

CHARLES CURTIS CLARKE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,269,442 Hoffman June 11, 1918 1,824,936 Travers Sept. 29,1931 1,888,464 Lofland Nov. 22, 1932 2,133,267 Ayers Oct. 18, 19382,289,258 French July 7, 1942- 2,357,096 Fireman Aug. 19, 1944 2,388,659Ryan et a1 Nov. 6, 1945 2,529,874 Hoak Nov. 14, 1950 FOREIGN PATENTSNumber Country Date 423 Great Britain Dec. 10, 1903 of 1903

1. THE METHOD OF PRODUCING A DARK BROWN IRON OXIDE WITH RED-BLACKUNDERTONE FROM AN IMPURE LIQUOR HAVING A FERROUS CONTENT WHICH COMPRISESADJUSTING THE PH OF THE IMPURE LIQUOR TO WITHIN THE RANGE PH 2-PH 6UNTIL A CRUD IS FORMED, SEPARATING THE CRUD, ADJUSTING THE PH OF THERESIDUAL LIQUOR TO ABOUT 9.6, ELEVATING THE TEMPERATURE OF THE LIQUOR TOABOUT 200* F., INTRODUCING AN OXIDIZING GAS INTO THE LIQUOR WHILEMAINTAINING PRESSURE ON THE LIQUOR OF ABOUT 30 POINTS PER SQUARE INCHUNTIL CONVERSION OF THE FERROUS CONTENT OF THE LIQUOR TO HIGHER IRONOXIDES IS COMPLETED, WASHING THE IRON OXIDES AND DRYING.